This invention relates to semi-synthetic cephalosporin antibiotic compounds. In particular, it relates to cephalosporin compounds wherein the cephalosporin bicyclic nucleus, the 3-cephem nucleus, is substituted in the 3'-position by isoquinolinium and substituted isoquinolinium, and in the 7-position with a 2-heterocyclic-2-oximinoacetamido group.
Cephalosporin compounds substituted in the 3'-position with a quaternary ammonium group have been known for some time. For example, cephalosporin CA (pyridine) was one of the first derivatives of cephalosporin C prepared by Abraham et al. following the discovery of cephalosporin C, Hale, Newton, and Abraham, Biochem. J., 79, 403 (1961).
Cephaloridine, the well-known clinical anti-biotic, is the 3'-pyridinium cephalosporin, 7-(.alpha.-thienylacetamido)-3-(pyridinium-1-ylmethhyl)-3-cephem-4-carboxy late. Recently, Heymes et al., U.S. Pat. No. 4,152,432, describe semi-synthetic cephalosporin antibiotics wherein the 7-position side chain is a 7-[2-(2-(aminothiazol-4-yl)-2-alkoxyiminoacetamido] group. More recently, Takeda, U.K. Patent Specification No. 1,581,854, describes syn-7-[2-(2-aminothiazol-4-yl)-2-methoxyimino]-3-pyridiniummethyl-3-cephem -4-carboxylic acid. O'Callaghan, et al., in U.S. Pat. No. 4,258,041, describe 7-[2-(2-aminothiazole-4-yl)-2-oximinoacetamido]-3-(pyridinium-1-ylmethyl)- 3-cephem-4-carboxylate antibiotics, and the corresponding compounds wherein the pyridinium group in the 3'-position is substituted with a carbamoyl group.
Because of the continuing need for improved antibiotic thereapy in clinical practice, the search continues for broad spectrum antibiotics with greater potency and minimal toxicity. The semi-synthetic cephalosporin antibiotics long have been recognized as broad spectrum antibiotics, and several have achieved clinical importance. Continued research with the cephalosporin antibiotics has centered of late with the development of antibiotics having higher activity against certain gram-negative microorganisms such as pseudomonas and those which produce .beta.-lactamase destructive of .beta.-lactam antibiotics.